Tuning device for flexible wall klystron



July 9, 1963 v F. L. SALISBURY 3,

' TUNING DEVICE FOR FLEXIBLE WALL KLYSTRON Filed Dec. 6, 1960 FIG.2

FIG.3

FIG.6

INVENTOR. FREDERICK L.SAL|SBURY United States Patent 3,697,323 TUNING DEVICE FOR FLEXHELE WALL KLYTRN Frederick L. Salisbury, Los Altos, (Salli, assignor to Varian Associates, Palo Alto, Calif, a corporation of California Filed Dec. 6, 1969, Ser. No. 74,043 14 Claims. (Cl. 315-513) This invention relates in general to high frequency electron emissive devices and more particularly to novel improved klystron structure which permits the construction of klystrons of relatively high powers and improved efliciencies and which are extremely small in size and light in Weight, yet rugged. V

Klystrons have become widely accepted as generators, multipliers, and amplifiers of very high radio frequencies and the electronic systems in present day use and planned for the future require klystrons of increasingly higher efliciencies and higher powers at higher frequencies. In accordance with well-known klystron theory, as the frequency of operation of the klystron increases, the physical size of the klystron producing such frequencies decreases due to the smaller cavity resonator sizes. However, decreasing the size of klystrons mitigates against higher power outputs and higher efficiencies because of the necessity for relatively large masses of heat conductive material to carry away the heat in such higher power electron beam devices. Also, even though the size of the klystron is decreasing, the requirement on ruggedness of the klystron hecomes more and more acute due to the end use of such high frequency klystrons. For example, high frequency sources in the K-band region are required for systems subject to rough treatment yet, because of the abuse to which the system is to be subjected, the radio frequency source producing such high frequency must be extremely rugged. The requirement of smaller sizes, on the one hand, and higher powers and efficiencies and rugged construction, on the other hand, are not ordinarily compatible and are noteasily met in practice. In addition to the requirements of high frequency and exceptional ruggedness,

the klystron in many instances must also be capable of being tuned over an appreciable band of frequencies rapidly and with ease, yet must be extremely stable against undesired drift in frequencies.

It is, therefore, the object of the present present invention to provide a very small, lightweight klystron for operation in high frequency regions with high power output and high efficiency and which is extremely rugged in construction to withstand abuse.

One feature of the present invention is the provision of a novel klystron constructed from a bare minimum of separate components assembled in a rugged unitary device capable of meeting the object of the present invention.

Another feature of the present invention is the provision of a novel klystron structure in which the main portion of the klystron consists of a large unitary body of heat conductive metal in which a cathode, one or more internal cavity resonators, and a reflector or collector electrode are located and one or more resonator gap tuner structures securely afi'ixed to the main bodywhich serve to adjust the resonator gap spacing, the tuner being arranged so that it creates a minimum of interference with the heat conduction from the tube body.

Still another feature of the present invention is the provision of a novel klystron device of the above featured type wherein the gap tuning is accomplished by a distortional force directed against a small surfaced, weakened section of the main body.

These and other features and advantages of the present invention will become more apparent from a perusal of the following specification taken in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of a novel reflex klystron embodying the present invention,

FIG. 2 is a longitudinal cross-section-view of the novel klystron taken along section iines 2-2 in FIG. 1,

FlG. 3 is a transverse cross-section view of the klystron taken along section lines 33 in FIG. 2,

FIG. 4 is a transverse cross-section view of a modification of the klystron of FiGS. 1-3,

FIG. 5 is a longitudinal cross-section view of a twocavity klystron oscillator embodying the present invention, and

FIG. 6 is a longitudinal cross-section view of a twocavity klystron amplifier embodying the present invention.

Referring now to PlGS. 1, 2 and 3 of the drawings, there is shown a preferred embodiment of the invention incorporated in a reflex klystron which comprises a main body 11 made from a large unitary block of metal of good heat conductivity, such as copper or copper plated steel, this main body ll having a multidiameter bore 12 extending therethrough.

Fixedly secured within one enlarged end of the bore 12 in the large body 11 is an electron beam gun 13 of conventional structure comprising a gun body envelope memher 114 vacuum sealed into the end of the bore 12, a cathode mounting stem 15 having a cathode button 16 mounted on the inner end thereof, and a filament 17 extending within the stem. Encircling the stem 15 and button in is a hollow cylindrical focusing member 18 for properly focusing the electrons which are emitted from the cathode button into a desired electron beam.

Fixedly secured as by brazing within the smallest diameter portion of the bore which lies within the block body ill is an annular anode member 19 including a re-entrant tube portion 21. Also fixedly secured as by brazing within this section of the body is a hollow cylindrical header 22 having a small centrally aligned opening therein which serves to cooperate with the opening in the re-entrant portion 21 in forming the cavity resonator gap of the klystrons internal cavity resonator. A C-shaped conductive member 23 is brazed in the bore 12 between the anode member 19 and header 22 and serves to define the side walls of the cavity resonator. A reflector stem 24 is mounted from the reflector end of the body ll, this reflector stem being fixedly secured in an annular insulating member 25 as of ceramic, which is vacuum sealed to an annular reflector mounting member 26 fixedly secured within the body 11.

Another small bore extends into the block body 11 from one side and has a pinch-off tube 27 brazed therein through which this klystron is evacuated, the tube 27 being pinched off and sealed closed after evacuation.

A substantially rectangular-shaped opening 28 is also located in one side of the block body lit and extends to an iris 28 in the internal cavity resonator, the opening 28 forming a waveguide output. Vacuum sealed over the outer end of this rectangular opening is a wave energy permeable material 29 such as ceramic. The block 11 has a plurality of screw holes 30 in its one surface, thus forming a waveguide flange by which this klystron is mounted on the output load circuit.

A novel tuner mechanism is employed for this klystron for varying the cavity resonator gap spacing. A bore 31 extends into the body 1] and terminates short of the bore 12 leaving a relatively thin wall section 32 at the end of the bore 31. A partially threaded sleeve 33 is secured, as by brazing, within the bore. A plate 34 is securely aflixed to, the wall section 32 and a tuning screw 35 is secured at its inner end to this plate 34 and extends outwardly into an actuating nut 36, a hollow cylinder provided with internal threads at its inner end for mating with screw 35. Actuating nut 36 is also provided with transverse compressible slots 37 normal to its axis of rotation. At its outer end, actuating nut -36 is provided with an access entry for a tuning tool such as an Allen wrench for imparting motion thereto which is thereby transmitted to tuning screw 35. The outer portion of the sleeve 33 is threaded to accommodate the external threads of tuner lock nut 38. Tuner lock nut =38 is provided with slots at its outer end to accommodate a locking tool and is hollow to allow passage therethrough of the tuning tool for actuating nut 36.

In assembly, locking nut 38 is screwed down upon actuating nut 36 and a clamping action occurs upon screw 35. It is noted that the clamping action occurs from two directions, first, from the outward end of nut 36 due to the inward force of locking nut 38 and, second, from the bottom or shoulder of the sleeve 33 which acts as a ground plane. These two opposite and equal forces act on the opposite sides of the threads of screw 35 and prevent backlash but allow subsequent tuning. Normally, this is done at the factory and resetting of locking nut 38 is not again required.

During initial assembly of this klystron, and before addition of the reflector assembly, the anode member 19 and the header 22 are inserted into and secured in the body 11 so that the resonator gap spacing is wider than normal, the resonant frequency of the cavity resonator being greater than the normal midrange frequency. A tool is then inserted into the body 11 from the reflector end of the bore to apply a force against the header 22 and bend the edge of the central hole in toward the re-entrant portion 21, thus narrowing the gap and lowering the cavity resonator frequency to approximately its midrange value. This initial tuning action leaves the header 22. bowed inwardly slightly.

After evacuating the klystron and with the electron beam traversing the klystron, further tuning is accomplished by means of the tuning screw 35. An inward movement of the screw 34 as a result of rotation of the actuating nut as results in a deflection pressure being exerted on the thin wall section 32 of the body 11 which bends and, in turn, forces the header wall 22 to buckle and decrease the resonator gap spacing. Outward movement of the screw draws the wall section 32 outwardly, causing the header to move outwardly of the cavity resonator and thereby increase the resonator gap spacing, thereby raising the resonator frequency. Since klystron operation is well known to those skilled in this art, explanation of the operation of this tube is not deemed necessary.

The tuning mechanism may be temperature compensated by making the screw 35 of a material having low temperature expansion characteristics such as Kovar or molybdenum. As the anode l9 and header 22., which are of material of relatively high temperature expansion characteristics such as copper, are heated up, they expand and tend to decrease the resonator gap spacing therebetween, resulting in a tendency to decrease the resonator frequency. The copper body 11 also expands, pushing the actuating nut 36 and screw 35 in a direction away from the cavity resonator, and since the screw 35 has low temperature of expansion characteristics and does not expand to the same degree as the body 11, the wall 32 is moved outwardly causing the header wall 22 to move away from the reentrant portion 21, thus tending to increase the resonator gap spacing to oflset the tendency to decrease the gap stated above.

It should be noted that other forms of tuning apparatus may be utilized as desired to exert the desired force against the wall section 32 for changing the resonator gap spacing.

This novel klystron construction renders a tube of very high frequencies with high efficiency and high power. Attainment of the unusually high efliciency and powers are due mainly to the fact that the very small cavity resonator is located within the heart of a very large block of heat conducting metal which serves to rapidly carry away the heat generated within the klystron. The large block is interrupted for tuning purposes only by the relatively small cylindrical opening 31 which extends into the block and terminates short of the cavity resonator stiucture. This permits a tuning force to be exerted directly in at the cavity resonator without interfering with the removal of heat from the interior of the unitary block body. Because of this unique tuning arrangement, it is possible to utilize a gridless cavity resonator gap thereby permitting higher powers to be generated and higher efiiciencies to be obtained with this klystron.

One reflex klystron embodiment constructed in accordance with the present invention operates in the band of frequencies of from between 33 to 34 kilomegacycles to between 35 and 36 kilomegacycles at a power output of over one watt.

In FIG. 4 there is shown a modification of the klystron of FIGS. 13 wherein two separate tuning means are shown, one tuner, the lefthand one, being similar to that shown in the preceding figures and the other tuner being a fixed tuner used especially for temperature compensation. A bore 31 is located in a wall of the body 11 and terminates short of the central bore 12', leaving a thin wall section 32' adjacent the bore 12'. A rod 35 of lower temperature expansion characteristics than the body Ill is secured, as by brazing, to the wall section 32 at its inner end and to a mounting plug 35 affixed to the body T1 at its outer end. This fixed tuning means functions as explained above for temperature compensation. The output waveguide 28 is located in a direction normal to the bores '31 and 3 Referring now to FIG. 5 there is shown in longitudinal cross section a portion of a two-cavity klystron oscillator embodying the present invention. In this embodiment the longitudinal bore 41 through the solid block body 42 has formed therein two cavity resonantors '43 and 44 with a feedback coupling hole 45 located in the header 46 between the two cavity resonators. As in the above described reflex klystron, tuning of the cavity resonators is accomplished by tuning screws 47 extending in toward the resonators through bores 48 for exerting a force upon the thin wall sections 4'9 adjacent the headers 51 of the two-cavity resonators and thus providing for resonator gap tuning in the two-cavity resonators as described above. Initial tuning of the two cavities of the oscillator is accomplished before the electron beam collector assembly 52 and cathode assembly are vacuum sealed on the tube by the insertion of a tool through both ends of the bore for bending the headers 51 slightly to obtain the desired initial resonator gap spacing. The output from the catcher resonator 44 is taken through the output waveguide 53 to the load circuit.

In FIG. 6 there is shown a two-cavity klystron amplifier embodying the present invention. The structure of this amplifier is similar to that or" the two-cavity klystrou oscillator of FIG. 5 (and bears similar reference numerals) With the exception that the coupling hole between cavities is omitted and that an input waveguide opening into the first or buncher cavity resonator through iris 43 is provided. Thus, two sides of the body have threaded holes therein for serving as waveguide flanges for coupling this amplifier to the input and output circuits. Tuning by means of the tuning screws 47 is accomplished in the manner described above.

Since many modifications in and variations from the described apparatus may be made without departing from the spirit of the invention, the foregoing embodiments of the invention are to be considered as exemplary and not in a limiting sense.

What is claimed is:

1. A klystron tube comprising a main body portion of solid metallic material having a bore therein, a cathode for supplying an electron beam in said tube axially through said bore, a pair of wall members positioned in said bore each having a centrally positioned electron beam permeable passage therein aligned with said cathode, the wall members being spaced apart and serving to form a cavity resonator in said bore and providing a resonator gap therebetween at said beam openings, said main body having an opening extending into one side thereof and terminating short of said bore so as to form a relatively thin wall section in the body at said bore adjacent one of said wall members, and tuning means positioned in said last opening and extending into contact with said thin wall section for permitting a force to be exerted on said thin wall section to thereby cause said one wall member to bend and change the resonator gap spacing between the two wall members.

2. A klystron tube as claimed in claim 1 including a reflector electrode positioned at the end of said cavity resonator opposite to said cathode for creating reflex klystron action in said klystron, said reflex klystron being tuned in operating frequency by said tuning means.

3. A klystron tube as claimed in claim 1 wherein said tuning means includes a screw member connected at one of its ends to said thin wall section.

4. A klystron tube as claimed in claim 1 wherein the length of the opening extending into the side of the body is greater than the surface length of the thin Wall section at the inner end of the opening.

5. A klystron tube as claimed in claim 1 wherein said tuning means includes a member connected at its inner end to said thin wall section and connected to said body at a point removed from said thin wall section, said member being made of a material having a lower temperature expansion coefiicient than said body to thereby provide temperature compensation in said klystron.

6. A mul-ticavi-ty klystron tube comprising a main body portion of solid metallic material having a bore therein, a cathode for supplying an electron beam in said tube axially through said bore, a plurality of Wall members positioned in said bore each having a centrally positioned electron beam permeable passage therein aligned with said cathode, the wall members being spaced apart and serving to form a plurality of cavity resonators in said bore, a collector positioned to collect the electrons in said beam after passage through said cavity resonators, said adjacent wall members providing a resonator gap in each of the cavity resonators, said main body having a plurality of openings extending into the body normal to said bore and terminating short of said bore so as to form relatively thin wall sections in the body at said bore each adjoining a wall member of an associated cavity resonator, said thin wall sections forming a part of the vacuum envelope of the tube, and tuning means positioned in said openings and extending into contact with said thin wall sections for permitting a force to be exerted on said thin wall sections to thereby cause said adjoining wall members to bend and change the resonator gap spacing of the associated cavity resonators.

7. A klystron tube as claimed in claim 6 wherein each said tuning means includes a screw member connected at one of its ends to said thin wall section.

8. A klystron tube as claimed in claim 6 wherein the length of the openings extending into the body is greater than the surface length of the thin wall section at the inner ends of the openings.

9. A klystron tube as claimed in claim 6 wherein said tuning means includes a member connected at its inner end to said thin wall section and connected to said body at a point removed from said thin wall section, said member being made of a material having a lower temperature expansion coefiicient than said body to thereby provide temperature compensation in said klystron.

10. The tube of claim 1 wherein said tuning means is capable of tuning said cavity resonator over an appreciable band of frequencies.

11. The tube of claim 6 wherein said tuning means is capable of tuning said cavity resonator over an appreciable band of frequencies.

12. The tube of claim 1 wherein said main body has a second opening extending into the other side thereof opposite to said first opening extending into one side thereof, said second opening terminating short of said bore so as to form a second relatively thin Wall section in the body at said bore adjacent the opposite side of said one of said wall members, said second thin wall section having means connected at its inner end to said second thin wallsection and connected to said body at a point removed from said second thin wall section, said means being made of a material having a lower temperature expansion coeflicient than said body to thereby provide temperature compensation in said klystron.

13. The tube of claim 1 wherein the tuning means is fixedly attached to said thin wall section.

14. The tube of claim 6 wherein the tuning means are fixedly attached to each said thin wall section.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A KYLSTRON TUBE COMPRISING A MAIN BODY PORTION OF SOLID METALLIC MATERIAL HAVING A BORE THEREIN, A CATHODE FOR SUPPLYING AN ELECTRON BEAM IN SAID TUBE AXIALLY THROUGH SAID BORE, A PAIR OF WALL MEMBERS POSITIONED IN SAID BORE EACH HAVING A CENTRALLY POSITIONED ELECTRON BEAM PERMEABLE PASSAGE THEREIN ALIGNED WITH SAID CATHODE, THE WALL MEMBERS BEING SPACED APART AND SERVING TO FROM A CAVITY RESONATOR IN SAID BORE AND PROVIDING A RESONATOR GAP THEREBETWEEN AT SAID BEAM OPENINGS, SAID MAIN BODY HAVING AN OPENING EXTENDING INTO ONE SIDE THEREOF AND TERMINATING SHORT OF SAID BORE SO AS TO FORM A RELATIVELY THIN WALL SECTION IN THE BODY AT SAID BORE ADJACENT ONE OF THE SAID WALL MEMBERS, AND TUNING 